Are root exudates more important than other sources of rhizodeposits in structuring rhizosphere bacterial communities?

Abstract

This review evaluates the importance of root exudates in determining rhizosphere bacterial community structure. We present evidence that indicates that: (1) the direct influence of root exudates on rhizosphere bacterial communities is limited to small spatiotemporal windows related to root apices; (2) upon rapid assimilation by microorganisms, root exudates are modified, independent of plant influences, before rerelease into the rhizosphere by the microorganisms themselves--thus, at short distances from root apices, rhizosphere carbon pools are unlikely to be dominated by root exudates; and (3) many of the major compounds found in root exudates are ubiquitous in the rhizosphere as they are found in other pools of rhizodeposits and in microbial exudates. Following this argument, we suggest that the importance of root exudates in structuring rhizosphere bacterial communities needs to be considered in the context of the wider contribution of other rhizosphere carbon pools. Finally, we discuss the implications of rhizosphere bacterial distribution trends for the development of effective strategies to manage beneficial plant-microorganism interactions.

Huanglongbing alters the structure and functional diversity of microbial communities associated with citrus rhizosphere

“…Plants are the key primary producers in most terrestrial ecosystems and generally exploit soils for resources using complex root systems (Dennis et al, 2010). The root exudates allow the maintenance of a dynamic and nutrient-rich niche around the root-soil interface called the rhizosphere (Curl and Truelove, 1986;DeAngelis et al, 2009).…”

“…The root exudates allow the maintenance of a dynamic and nutrient-rich niche around the root-soil interface called the rhizosphere (Curl and Truelove, 1986;DeAngelis et al, 2009). The diversity of nutrients and plant secondary metabolites present in the exudates allows enrichment of specific taxonomic or functional groups of bacteria in the rhizosphere (Bais et al, 2006;Haichar et al, 2008;Dennis et al, 2010). Microbial populations in the rhizosphere are immersed in a framework of interactions known to affect plant fitness and soil quality (Nannipieri et al, 2003;Lugtenberg and Kamilova, 2009).…”

Stability and succession of the rhizosphere microbiota depends upon plant type and soil composition

“…The rhizosphere is a critical zone of soil surrounding roots that is directly influenced by the plant and into which plants secrete as much as 11% of net fixed carbon (Jones et al, 2009;Dennis et al, 2010). It is a 'hot spot' of microbial activity, with increased microbial numbers, microbial interactions and genetic exchange (Bulgarelli et al, 2013;Turner et al, 2013a).…”

Spatio Temporal Influence of Isoflavonoids on Bacterial Diversity in the Soybean Rhizosphere

“…Such changes are attributed to the rich carbon energy sources provided by the plant. Indeed, plants release, on average, 10 to 15% (Jones et al 2009) of their photosynthetic assimilates into the rhizosphere, a process called rhizodeposition (Dennis et al 2010). These rhizodeposits originate from sloughed off root border and root border-like cells from root tips, active root exudation, and cell lysis.…”

“…These rhizodeposits originate from sloughed off root border and root border-like cells from root tips, active root exudation, and cell lysis. Rhizodeposits are composed of sugars, amino acids, organic acids, fatty acids, proteins, ions, secondary metabolites, mucilage, water, and miscellaneous carbon-containing compounds (Bais et al 2006;Dennis et al 2010). …”